Servomotor



R. H. HILL l sERvoMoTon Aug. 26, 1947.

Filed Dec. 17, 1942 3 Sheets-Sheet 1 R. H. HILL -savouowon Filed Dec. 17, 1942 /z l l-)Wf 73xl Aug. 26, 1947.

5 Sheets-Shea't 5 ffy 2:?

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Patented Aug. 26, 1947V 2,426,505 ssnvoMo'ron Robert H. Hill, Anderson, Ind., assignor to General Motorscorporatlon, Detroit, Mich., a corporation ot Delaware Application December 17, 1942,y Serial No. 469,304

` (oi. 19a-.02)

3 claims. l

This invention relates to servo-mechanisms operated by electric motors whereby mechanical movements may be eiected by remote control. For example, the present invention is concerned with servo-motors for operating the steering mechanism of an airplane.

It is an object of the present invention to provide a unitary structure comprising an electric motor, speed reducing gearing connecting the motor with a shaft which is connected by a magnetie clutch with an operating arm, relay switches for controlling the operation of the motor in a forward or reverse direction, limit switches for rendering the motor non-operative when the operating arm has moved a predetermined extent in either direction and means for braking the motor when the motor becomes non-operative.

Further objects and advantages of the present invention wili be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

Fig. 1 is a longitudinal sectional view of a servomotor unit embodying the present invention.

Fig. 2 is a fragmentary view showing a portion of Fig. 1, on an enlarged scale.

Fig. 3 is a sectional view on line 3-3 of Fig. i.

Fig. 4 is a left end view in the direction of arrow 4| of Fig. 1.

Fig. 5 is a view on line 5--5 oi Fig. 1, the parts to the left on the line 5--5 having been removed.

Fig. 6 is a sectional view on the line 6-6 of Fig'. 5.

Figs. 7, 8 and 9 are sectional views taken respectively on line 6--8 and 9 9 oi' Fig: 1.

Fig. 10 is a right end view in the direction of the arrow it ci Fig. 1, the end cover being shown in section.

Fig. 11 is a fragmentary right end View 'with the cover removed showing a modified arrangement of the limit switches.

Figs. 12 and 13 are wiring diagrams.

'I'he unit comprises a frame member 26 for enclosing speed reducing gearing and a magnetic clutch. Frame is closed at its right end by a plate 2| for supporting limit switches. The left end of frame 26 is enclosed by a plate 22 which supports shaft bearings and which provides the right end Wall of an electric motor M. Frame 22 provides the right end cover for a magnetizable field frame 23 associated with a left end cover provided by frame 24 which provides a chamber 25 for the commutator and brushes of the motor and a chamber 26 for enclosing terminal members connected with the motor field and armature circuits. 'I'he frame members 22 and 2l support bearings 3|! and 3| for an armature shaft 32 supporting an armature 33 and a commutator 34. The armature revolves between pole pieces one of which is shown at 35. Each pole piece is surrounded by a. winding assembly comprising a shunt field 36 of relatively fine wire and a, series field 31 of relativelyn coarse wire. The commutator 36 is engaged by brushes 36 and .39 (Fig. 7) supoorted on studs t@ and Si respec- "i rv he me 26%.

ure shaft ugh a nonmagnetizable sleeve 5| which slides oug'h the central bore in the hub 52 of bien.; disc 53. Hub 52 has iongitudinai splines, 5K3 receiving ends of the pin M; and thus the pin 5@ drivingly connects the shaft 32 with the brake disc huh 52. The stationary brake member is provided by a disc 55 attached to the frame 2d and providing a cover for the housing 26. Between the disc and the rotatable brake disc 53 there is located a leather disc 56. The braie parts are normally held in engagement by a spring 6U which is confined between a nut di on the threaded end 62 of shaft 32 and a washer @E which is reved by a recess Sii in the ieit end of brake disc hub 52. Between nut iii and washer o3 there is located a spacing sleeve 65 less in iength than the normal distance between nui; 6| and Washer 63. The disc 53 is caused to separate from the disc 55 by an electromagnet of which the disc 53 and its hub 52 provide the armature. Hub 52 is guided :for horizontal movement 'oy a nonconducting tube 'lli supported by a tubular boss 1| of o. cup-shaped magnetizable housing 'it which encloses a magnet coli 'E3 supported by' the tube Iii and insulated therefrom. The coil i3 is retained by a washer il against which a portion of the housing 'i2 is staked as indicated at 15. The tubular boss 1| has an opening 'iii through which the shaft 32 extends. The nut 6| is protected by a plug il screwed into the threaded counter-bore 'i6 of [the brake magnet housing 12. The location of the nut 6| relative to the shaft 32 determines the spacing between the nut 6| and the washer 63 which spacing is greater than the length of the sleeve 65. Therefore, the location of the nut 6| determines how far the fbrake magnet armature provided by disc 53 will move Ibefore the sleeve is contacted both by the washer 62 and by the nut 6|. Thus the location of the nut 6| determines the minimum aia-gap between the brake disc 53 and the adjacent peripheral portions of the brake magnet housing 12 and also the minimum air-gap between the central boss 1| of the housing 'l2 and the hub 52 of the brake disc. The adjustment of the nut 6| should be made in order that this gap will be made as small as possible, but 'Without having the armature provided by brake disc 53 and its hub 52 striking any stationary part of the magnetic circuit. The leads of the coil 13 pass through a cable sheath 19 into the chamber 26 which is covered also by a plate 60 having a hole 6| through which wires lead to a current source and to remote control apparatus which may be connected to the servo-motor unit.

At its right end the armature shaft is secured by a pin 90 to a gear 9| which meshes with the gear 92 fixed to a hub 93 having a gear 94 mesh ing with a gear 95 fixed to a hub 96 providing a gear 91 meshing with a gear 96 fixed to a hub 99 providing a gear |00 meshing with a gear |6| iixed to a hub |02 providing a gear |03 meshing with a gear |04 provided by magnetizable shaft |05 journalled in a non-niagnetiaable bearing |06 supported by a magnetizable clutch magnet frame |01 and journaled within the inner race of a ball bearing |06 supported by a frame 22. The gear hubs 96 and |02 rotate on a fixed shaft or rod lill having its right end received within an opening in frame and having its loft end integral with a cup-shaped bracket i I2 secured by screws ||3 to frame 22. The cupshaped member ||2 is cut away at ||4 to permit the meshing of gears 9| and 92. The hole I in the i'rame 20 is closed by aplug ||5.

The electromagnetically operated clutch comprises a magnetizable frame provided by a ring |20, the disc |01 and the shaft |05. The arma ture of the electromagnet is provided by the hub |2| of a magnetizable disc |22. The magnetizable ring |20 encloses an annular clutch magnet coil |24 supported by a nonmagnetizable sleeve |23 and insulated therefrom. The leads |24 and |25 of the coil |24 extend out through openings in the enclosing parts as shown in Fig. l. The magnetizable armature provided by hub |2| and disc |22 slides upon a non-magnetizable shaft |30 which is received by the central bore of the shaft |05 and has its left end portion |3| journaled in a bearing bushing |32 which is supported within the left end of shaft |05. Near its right end the shaft is supported by a bearing sleeve |33 carried by the tubular boss |34 of the plate 2| which covers the right end of the frame 20. Shaft |30 supports a washer |35 and has a splined portion |36 upon which a hub |31 is slidably mounted. Hub |31 has a flange |36 through which pass rivets |39 for securing to the ange a flexible metal disc |40 which carries near its periphery a plurality of equally spaced eyelets |4 Through each eyelet there extends a stud |42 attached to the disc |22. It is therefore apparent that the disc |22 drives the disc |40 through the studs |42 and eyelets |4|. Normally the discs |22 and |40 are spaced relatively close together as shown in Fig. 1, this spacing being maintained by a plurality of springs |43 each confined under compression between disc 40 and a. washer |44 which is retained by a pin |44a extending through a stud |,45 fixed to disc |22. These springs |43 urge the disc |22 toward the right until it engages the washer |35. |22 three equi-distant pins |46 attached to hub |2| are retracted from three of nine equi-distant holes |41 of shaft |05 (Fig. 3). When the clutch magnet coil |24 is connected with a suitable CUI- In this position of disc v f Shaft |30.

rent source, the disc |22 is attracted toward the ring |20, thereby causing the pins |46 to engage the right end of shaft |05 which, then being in a state of rotation, causes certain of the holes 41 to be brought into alignment with the pins |46 so that the left ends of these pins will move into the holes |41 then in registry therewith. In this way, the shaft |05 is connected with the disc |22. Therefore `the electric motor is connected with shaft |30 through the speed reducing gearing and through the clutch elements |05 and |46 of a magnetically controlled clutch and through the pins |42 and eyelets |4| and disc |40 connected with hub |31 which is splined at |36 to the When the clutch magnet coil |24 is disconnected from the current source, the springs |43 move the disc |22 toward the right and retract the pins |46 from the shaft |05.

Referring to Fig. 12 it will be seen that the apparatus provides terminals 13x, 31x, 36x and 391: for making connections with different parts of the apparatus and that the apparatus provides terminals |50, |5|, |52 and |53 to be connected with the external circuits. Terminal |50 is connected with a wire |50a and with battery |55. Terminal |53 is connected with a switch |56 having a ground return |51 to the battery. Terminals |5| and |52 are connected, respectively, with relays |6| and |62 having electromagnets |63 and |64, respectively, which may be energized in any suitable manner by connecting them with a current source either by a manually operated switch or by some remote control such as operated by radio. The relays |6| and |62 control pairs of contacts and |66, respectively, for connecting wire |50a and battery |55 with the terminals |5| and |52, respectively.

Terminals |5| and |52 are connected with limit switches |61 and |68 respectively, comprising pairs of normally closed contacts |61a and |66a respectively, which are normallyy engaged and which are separated, respectively, by the engagement with resilient arms |61b and |66b, respectively, of a roller |69 mounted on a stud |10 extending through an arcuate slot |1| in frame 2| and attached to disc |22, see Figs. 1, 10 and 11. Figs. 10 and 11 show different arrangements of the limit switches |61 and |66 with reference to the roller |69. The spacing between the arms |61b and |68b determines the maximum movement of the shaft |30 in either direction and of the arm |46 attached thereto by a key |46b and a clamping screw |46a (Fig. l).

The limit switches |61 and |66 are connected, respectively, with magnet coils |11 and |16, respectively, of relays |15 and |16. These magnet coils are connected by wires |19 and |60 with the terminal |53. Relays |15 and |16 have similar armatures |6| and |62, respectively, connected with generator brushes 36 and 39, respectively, and normally separated from the magnet cores from the magnet cores |11a and |16c, respectively. Armature |8| carries contacts |63 and |61 adapted to engage contacts 65 and |69, respectively, but normally out of engagement therewith. Contact |61 is insulatingly supported by the armature |6|. Armature |6| carries a contact |9| normally engaging a, contact |93. Armature |62 carries contacts |64 and |66 adapted to move into engagement with contacts |66 and |90, respectively, but normally out of engagement therewith. Contact |66 is lnsulatingly supported on armature |62. Armature |62 carries a contact |92 normally engaging a. contact |64. Contacts |33 and |94 are connected by wire |6| connected at 31a: with the series field coil 31 which is connected through an adjustable resistance |96 with terminal |50. Contacts |81 and |88 are connected by flexible leads |91 and |98, respectively, and by wires |99 and 200, respectively, with a terminal 13a: of a brake magnet coil 13 which is connected with wire |50a. Re-

lay contact |89 and |85 are connected by wireV 20| with the terminal |53. Relay contacts |86 and |90 are connected by wire 202 with the terminal |53. The shunt field coil 36 and th'e clutch magnet coil |24 are connected in parallel and with the wire |50a and with wire 202 leading to terminal |53.

When the manual control switch |56 is closed, the shunt field winding 36 and the clutch coil |24 are connected with the battery |55. If the contacts |65 are closed manually or by a remote control acting through the relay magnet coil |63, the magnet coil |11 of relay |15 becomes energized and armature 8| moves downwardly to disconnect contact |9| from contact |93 and to cause the engagement of contacts |83, |85 and |31, |69, thereby causing the brake magnet coil 13 to become energized to release the brake by moving disc (Fig. l) away from disc 55 and to cause the following armature in series field circuit to be established: ground |51, switch i56, wire 20|, contacts |85, |83, relay armature blade |8|, brush 38, armature 33, brush 39, relay armature blade |82, contacts |92, |94, wire |95, series field 31, variable resistance |96, terminal E50, battery |55 and ground |51. This circuit causes the electric motor to drive the shaft |30 in a. clockwise direction as viewed in Fig. 10 and this motion will continue so long as the contacts |65 remain closed but no longer than the limit switch l61 remains closed, this switch being opened by the engagement of the roller |69 with the blade |61?) when said roller moves in a clockwise direction past the position shown in full lines in Fig. 10. When contacts |65 are opened or when limit switch contacts |61a are opened, rotation of the motor in a direction to cause clockwise rotation of shaft |30 ceases since relay |15 is deenergized and armature blade |8| returns to position shown, thereby causing a short circuit of the armature 33 of the electric motor through the wire |95 which connects With the closed pairs of contacts |9|, |93 and |92, |94. Separation of contacts |81, |89-causes the brake coil 13 to be deenergized thereby permitting the brake discs 55, 56, 53 to re-engage under the action of spring 60 (Figs. 1 and 2).

When contacts |66 are closed by manual operation or by remote control operating through relay magnet |64, relay |16 becomes energized and armature |82 moves down to separate contact |92 from contact |94 and to effect the engagement of contacts |84, |86 and |88, |90, thereby rendering the brake coil 13 effective to separate the brake discs and thereby completing the following armature and series field circuit of the electric motor: ground |51, switch |56, terminal |53, wire 202, contacts |86 and |84, blade |82, brush 39, motor armature 33, brush 38, blade 18|, contacts |9| and |93, wire |'95, series neld 31, variable resistance |96, terminal |50, battery |55, ground return |51. Since the direction of current through' the armature is now reversed, the armature will turn in such direction as to cause the shaft |30 to move counterclockwise. Such rotation of shaft |30 will continue so long as contacts |66 are closed, but no longer than limit switch |68 remains closed. Limit switch |68 will be opened when the roller |69 moves to the right of the position |69b (Fig. 10). The separation of either pairsv of contacts I 66, |68a will cause the deenergization oi relay |18' and the circuits will return to normal status shown in Fig. 12, thereby short circuiting the armature 33 and rendering the brake magnet coil 13 ineffective to maintain the brake discs out of engagement. The motor M will be stopped by dynamic braking due chiefly to short circuiting of the armature and, to some extent, by the engagement of the brake discs by the action of spring 60. The brake operates to prevent drifting of the operating arm 48 while the motor is not operating.

For certain applications of the servo-motor unit it has been found that frictional resistance issuflicient to prevent drifting of the operating arm. Therefore the electro-magnetically controlled brake can be omitted. When the brake coil is omitted, the diagram of circuits will be as shown in Fig. 13.

The relays |15 and |16 are mounted upon a bracket 2|0 secured by screws 2|| to a bracket 2|2 which is supported by a flat surface 2|3 provided by the housing 28. The limit switches and relays are enclosed by sheet metal shield members 220er and 22o?) attached to the frame Wall 2| to the bracket 2 l2 in any suitable manner. A tube 222 connects the space 223 Within the shield 220 with the space 26 within the frame 24; and the tube 222 provides a housing for any wires which may be used to connect the relays, A

limit switches and clutch magnet coil |24 with the various terminals according to the diagram, said terminals being located within the comparte ment 26. The terminals 13.11, 31m, 38s: and 39a: for interconnecting the parts of the unitary structure and the terminals i50, |5|, |52 and |53 for making external connection with the current source and control switches may be arranged as shown in Fig. 5.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. The combination with an electric motor, of a driven shaft; speed reducing gears driven by the motor; two discs, one anchored to the shaft, the second slidably mounted on the shaft; means anchored to the one disc and engaging the other disc to cause their concurrent rotation and permitting the second disc to slide toward and away from the first disc; means on the second disc engageable with a speed reducing gear to connect the motor with the shaft; and an electrcmagnet, energizable for moving the second disc away from the first and into engagement with a speed reducing gear.

2. The combination with an electric motor, of a member to be rotated thereby; speed reducing gearing operatively connecting the motor with said member; a shaft upon which said member is journalled; two discs, the flrst anchored to the shaft, the second slidable on the shaft and having means engageable with said member when said second disc is moved away from the first; means yieldably urging the second disc toward the rst and out of engagement with said member; and electromagnet means, energizable with the electric motor, for moving the second disc into driven engagement with said member.

3. The combination with an electric motor,

7 of a member to be rotated thereby; speed reducing gearing connecting the motor with said menuI ber; a shaft upon which said member is iournalled; two discs, the iirst anchored to, the second slidably on said shaft; pins anchored to one of said discs and slidably extending through holes in the other disc, certain of said pins having springs normally urging the discs toward each other; means on the slidable disc engageable with the member for connecting the motor with the shaft; and an electromagnet, energizable to attract and move the slidable disc away from the other disc and into operative engagement with the member.

ROBERT H, HILL.

REFERENCES CITED The followingl references are of record in the 111e of this patent:

Number UNITED STATES PATENTS Name Date Mellon Mar. 5, 1935 Harwood Nov. 19, 1929 Gross Abr. 21, 1936 Townsend et ai. Nov. 6, 1917 Vallen May 8, 1928 Jones July 31, 1928 Erwin Sept. 12, 1933 Shaw Mar. 16, 1943 Lear et al. Dec. 23, 1941 Buckley Sept. 17, 1940 Doll Aug. 1, 1944 

